Apparatus and methods for treating vascular conditions, and more specifically, materials for use in treating such conditions, are described.
Stent-graft assemblies may be used to treat a number of medical conditions. One common use of stent-graft assemblies relates to the treatment of an aneurysm, which is an abnormal widening or ballooning of a portion of an artery that may be caused by a weakness in the blood vessel wall. Another common use relates to the treatment of an aortic dissection, a tear in the inner wall of the aorta that causes blood to flow between the layers of the wall of the aorta and force the layers apart. If the dissection tears the aorta completely open (through all three layers), massive and rapid blood loss occurs. In many cases, the internal bleeding is so massive that a patient can die within minutes of an aneurysm or dissection rupture. For example, the survival rate after a rupture may be as low as 20%.
In an endovascular treatment of a blood vessel using a stent-graft, the stent-graft is positioned in the blood vessel across the aneurysm, e.g., using catheter-based placement techniques. The stent-graft treats the aneurysm by sealing the wall of the blood vessel with a generally impermeable graft material. Thus, the aneurysm is sealed off and blood flow is kept within the primary passageway of the blood vessel. Similarly, stent-grafts treat dissections by closing up the tear and flow is kept within the primary passageway of the blood vessel. Although stent-grafts are frequently used for treating aneurysms, other medical treatments also use stent-grafts and still other uses are possible, such as uses for stenosed arteries or other conditions.
Various types of stent-grafts are constructed with a stent disposed inside graft material, outside of graft material, or between inner and outer layers of graft material. The stents commonly are coupled to the one or more layers of graft material, by various methods.